If you're using REAPER to create your tracks, just follow the directions below to export them as 320 kbps MP3 files.
Click File in the top left corner and select Render. A Render to File window will pop up within the program. In that window, find the Output format section and choose MP3 from the drop-down menu.
When you do that, you may see a button that says "LAME unavailable." To fix that, you'll need to install the LAME encoder software so that REAPER can render your file as an MP3. You will only have to complete this process once. If you do not see the "LAME unavailable" message, you can skip the bulleted section below.
If you see the "LAME unavailable" button, click it and the MP3 Encoder Configuration window will appear. In that pop-up, click the link that says "Download LAME."
You'll be redirected to a page where you can download LAME from a list of files.
To select the right file, you'll need to know if you're using a 32 or 64 bit version of REAPER. When you know your version, click the appropriate link to download the LAME file.
Head to your Downloads folder on your computer and click on the file. Select "libmp3lame.dll" and copy it.
Head back to REAPER and in the same MP3 Encoder Configuration window, click the second link, which should begin with "C:\" - that will open a new UserPlugins folder.
Paste the "libmp3lame.dll" that you copied into that folder.
Head back to REAPER and, in the MP3 Encoder Configuration window, click "Try to reload LAME library."
Once you do that, REAPER will be all set to render MP3s.
Back in the Render to File window, ensure that your Mode (found under Output format) is set to "Maximum bitrate/quality." This automatically sets your bitrate to 320 kbps. In that same Render to File window, you can use the Directory field at the top to choose where the file will download to on your computer.
When that's all set, just click the "Render file" button at the bottom of the Render to File window. Once you do that, you'll have a 320 kbps MP3 that's ready to upload to Digital DJ Pool :)